Some internal combustion engines utilize a compression device such as a turbocharger to increase engine torque/power output density. In one example, a turbocharger may include a compressor and a turbine connected by a drive shaft, where the turbine is coupled to an exhaust manifold side of an engine and the compressor is coupled to an intake manifold side of the engine. In this way, the exhaust-driven turbine supplies energy to the compressor to increase the pressure (e.g. boost, or boost pressure) in the intake manifold and to increase the flow of air into the engine. The boost may be controlled by adjusting the amount of gas reaching the turbine, for example with a wastegate. An actuator may be operatively coupled via a linkage to a wastegate valve and driven to position the wastegate valve anywhere between a fully open position and a fully closed position (e.g., at a valve seat) to achieve the desired boost based on operating conditions. The actuator may be an electric actuator such as an electric motor, for example.
In some scenarios, the electric motor may be exposed to high surrounding temperatures due to proximate flow of exhaust gasses, and may exhibit high temperatures itself, for example due to the continuous reception of high electrical currents—e.g., during operating conditions in which high or maximum boost is continually desired. As such, estimation of the electric motor temperature may be desired to avoid degraded motor operation and potential motor degradation.
U.S. Pat. App. No. 2013/0312406 describes a method for controlling an electric actuator for a wastegate valve arrangement of an exhaust gas turbocharger. In particular, a temperature of the electric actuator may be estimated from an engine voltage supplied to the actuator and its operating current based on a calculation model.
U.S. Pat. No. 7,006,911 describes a system for estimating the temperature of an electric actuator. In one example, the electric actuator temperature is estimated based in part on a resistance temperature coefficient which represents a motor winding resistance.
The inventors herein have recognized several issues with such approaches. First, estimates of the temperature of an electric motor based on voltage and currents supplied to the motor may be inaccurate and in some scenarios may result in underestimating the temperature, which could lead to degraded motor operation and thus degraded boost control. Second, motor temperature estimates that use a single winding resistance may also result in inaccurate temperature estimation and thus potentially degraded motor control, as winding resistance in an electric motor is dependent on rotor position.
As such, measurement of the winding resistance of an electric motor at multiple rotor positions may increase the accuracy of motor temperature estimation. However, the rotor will undergo frequent rotation under typical operating conditions, making measurement at multiple positions impractical as a non-negligible finite duration (e.g., 100 ms) may be required for a single winding resistance measurement.
Methods for estimating electric actuator temperature during certain operational windows are thus provided.
In one example, a method comprises adjusting an electric motor to position a wastegate at a desired wastegate position, while during selected conditions, deviating from the desired position by at least one full half-turn of the motor and indicating motor temperature based on winding resistance averaged over the full half-turn.
In a more specific example, the selected conditions include maximum boost in which the wastegate is placed at a fully closed position.
In another aspect of the example, the selected conditions include minimum boost in which the wastegate is placed at a fully open position.
In yet another aspect of the example, during the selected conditions the desired wastegate position is a constant partial lift.
In still further another aspect of the example, the method further comprises if the motor temperature exceeds a threshold, reducing current supplied to the motor.
In the examples described above, the accuracy of electric actuator temperature estimation may be increased, which may increase the accuracy of, and avoid degradation of, operation of the electric actuator. Thus, the technical result is achieved by these actions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.